Indurated fibrous material and process of making the same



Mafch 2, 1943. A. ELMENDORF 1..

INDURATED FIBRO US MATERIAL AND PROCESS OF MAKING THE .SAME

Filed June 22, 1940 Patented Mar. 2, 1943 INDURATED FIBROUS MATERIAL ANDPROC- ESS OF MAKING THE SAME Armin Elmendori', Wlnnetka, 111.Application June 22, 1940, Serial No. 841,809

15 Claims.

Artificial boards or panels of the low density, fibrous insulation boardtype. cannot successfully be employed in buildings or other structuresin places where the characteristics of hardness, stiffness andresistance to weather found in wood are required. The primary object ofthe present invention is to make it possible to use this type ofmaterial in many places for which it has not heretofore been availableby providing boards or panels composed thereof, at a reasonable cost.with faces that are hard and tough, that are much more weather-resistantthan are the virgin faces, which readily take paint and which add verysubstantially to the stiffness of the boards or panels.

In the expectation that if a fibrous board could be impregnated, inwhole or in part with a suitable water-proofing material that wouldharden and give strength and stiffness to a board, I experimented withmany induratlng substances and discovered that some which may beincluded in the description hardwood pitch possess the necessaryproperties, provided that they can be successfully introduced into theboards. Hardwood pitch which may be the result of vacuum distillation ofhardwood tar and has a melting point, by the cube in air method, of from90 C. to 100 C., or a pitch which is a condensation of heavy phenolicwood oils with certain aldehydes occurring in the pyroligneous acid andwhich has a melting point of from 105 C. to 110 C., may be used. But, ifthe pitch is simply melted, it will not penetrate the fibrous materialwhen applied thereto in any usual way, as by submersion. When it isattempted to effect penetration by giving to the pitch a temperaturesubstantially above the melting point, it is largely converted intovapors which are dissipated in the atmosphere and only a charred residueis left on the surface of the fibrous materials. As I have succeeded incausing hardwood pitch to penetrate into the interior of low densityfiber board, in a simple and inexpensive manner, what I have done may beregarded, in one of its aspects, as a discovery of a novel method ofindurating porous, fibrous materials, such as insulation boards orporous sheets of which kraft paper is an example, with hardwood pitch.

I have found that by pulverizing solid hardwood pitch and spreading alayer of the powdered pitch upon the surface of a board or panel, thepitch may be driven-into the latter by means of heat and pressureapplied while the pitch is confined in contact with the board or paneland is prevented from escaping into the surrounding atmosphere in theform of fumes. In the case of large boards or panels, the confining ofthe pitch and the fumes evolved therefrom may be effected by simplylaying a caul on top of the layer of powdered pitch and applying theheat and pressure through this caul, The caul may be a metal plate ofthe same area as the board or panel, or it may simply be one of theplatens of a hot press. The pitch must be heated to a temperature muchhigher than the melting point of the pitch, so that the pitch becomesvery fluid and is vaporized to some extent. A little of the liquid mayooze out from between the caul and the board or panel around the edgesbut, in the case of large commercial panels and boards, the loss fromthis is so small as to be almost negiigible.

In the case of a pitch having a melting point of C., I have found thatwhen the process is carried out at a temperature of C., the pitch doesnot pass into the board or panel but remains on the surface. However, ata temperature in the neighborhood of 190 C., good penetration is securedin about four minutes; the time required to effect successfulpenetration in creasing with a decrease in the temperature below 190 C.Temperatures up to about 260 C. have been employed satisfactorily,Pitches having a melting point around 95 C. cannot be driven intofibrous insulation boards at temperatures below 140 C., but must beheated to higher temperatures. Thus, at a temperature of C., good,penetration can be obtained in about three minutes. As the temperatureis lowered below 175 C., the time required to secure proper penetrationincreases. The temperatures of C. and 175 C., here given, are what maybe termed optimum temperatures, a considerable range in both directionstherefrom being permitted.

Subjected to these high temperatures, while exposed to atmosphere, thevolatile matters of the pitch are driven off in the form of vapors andonly a charred residue remains. In the carrying out of my process vaporsare evolved but, since they cannot escape in any other direction, theypass into the porous board or panel, carrying with them or driving aheadof them such portion of the pitch as still remains in liquid form. Theresult of the treatment of the board or panel is to drive practicallyall of the pitch into the interior of the latter, no coating in the formof a film or flakes being visible on the surface of the material whenremoved from the press. Furthermore, when the impregnated portion of thetreated material is examined under the microscope-it is apparent thatthe pitch does not" enter the board by simply filling the voids in thefiber board and thus forming tiny pools, because the voids still remainand thedissipation of the pitch .is shown as having occurred in the formof coatlugs for the individual fibers.

the impregnated portion of the fiber board material has very-much theappearanc ofhavlng been formed or manufactured from coated fibers.

In carrying out the process, no great amount of external pressure ispermitted because the board must not be crushed, as it is desirable toretain the insulating value of the original board; In the case of aboard or panel thatis originally three-quarters of an inch thick,there'is apparently no advantage in exerting a greater pres- In fact,the characteristics of boards or panels treated in accordance with myprocess are such thatthe indurated sides may be exposed to the weatherin sidings for buildings or other structures, because they areweather-resistant and are tough and stifi enough to withstand the usualpressures and blows which they may be expected to receive. While theimpregnated portion of the fiber board material is not entirelywaterproof, yet it is much more so than the virgin fiber board materialbecause each fiber is waterproofed. Also, since the impregnated surfacewill take paint readily, ability to resist the en trance of water needdepend only on the use of a good paint, since the siding as a whole willbe as resistant to the entry of water as is the paint itself.

After the material leaves the hot press and cools, it appears to have apermanent shape which does not appreciably change under normal changesin temperature and atmospheric humidity. For example, if the board orpanel be fiat, after it has become cool, it afterwards remains flat.Since the fibrous boards or panels are flat before they are subjected tothe indurat ing process, it is only necessary that they be kept fiatimtil they havie cooled after induration. Often if a panel is removedfrom thepress and permitted to cool without being restrained, it warpsin cooling and thereafter remains warped. I have found that thisobjection can be overcome by constraining the board or panel while it iscooling, conveniently by transferring the panel directly from the hotpress to a cold press which then keeps the panel fiat until it hascooled and the pitch has hardened.

Sheets of paper for facing wood cores-can also be treated in the sameway as boards, although in the case of paper sheets the induratingmaterial extends throughout substantially the entire thickness of thesheets. Sheets can conveniently be treated as they are unwound fromrollers and be then rolled'up again until they are to be used.Furthermore, two sheets at a time may be impregnated, each serving as acovering member or caul for the other. For example, two sheets thatoverlie each other and between which In other words;-

between hot pressure rolls. It is found that the pitch'passes in aboutequal amounts into both sheets and, curiously, upon cooling, there is nobonding together of the sheets which simply lie in contact with eachother at the discharge end of the apparatus and can therefore be rolledup separately. Viewed in one of its aspects, the present invention ordiscovery may therefore be said to havefor an object a simple method ofimpregnating sheets of paper with hardwood pitch or the like.

In the accompanying drawing I have illus-' fibrous insulation boardtype; Fig. 2 is a view there is a layer of hardwood pitch, may be fedsimilar to Fig. 1, showing a layer of hardwood pitch overlying a face ofthe board or panel; Fig. 3 is a view similar to Figs. 1 and 2, showingthe board or panel after it has been treated in accordance with thepresent invention; Fig. 4 is a view showing a fragment of a hot presscontaining the board or panel with its layer of pitch as illustrated inFig. 2, on a smaller scale than Fig. 2; Fig. 5 is a cross-sectional view.showing a fragment of the side of a building provided with aninsulating siding composed of my improved boards or panels; Fig. 6 is aview similar to Fig. 3, illustrating a board or panel indurated on bothsides; Fig. 7 is a perspective view of a corner of a panel comprising awood core faced on both sides with impregnated sheets of paper; and Fig.8 illustrates diagrammatically a method of impregnating ,two sheets ofpaper simultaneously.

Referring to Figs. 1 to 4, I represents a board or panel of the lowdensity insulation board type such, for example, as the material knownas Celotex. Porous boards made of wood wool or fine excelsior. bondedwith'mineral cements may be used. Where it is to be used as a substitute forsheathing and siding in a wooden building, the board or panelmay be of a usual commercial type that has a thickness of aboutthree-quarters of an inch. Usually it would be sufiicient to induratethe board or panel from one side only, namely the side that is to beexposed to the weather. In that case the board or panel may first haveapplied thereto a layer 2 of hardwood pitch, preferably in powdered formabout one-tenth of an inch thick, as shown in Fig. 2. The board or panelis then subjected to heat and pressure, while the pitch is kept coveredso that the fumes that are generated cannot escape to any extent, exceptinto the interior of the board or panel. The cover or caul may take anysuitable form, depending upon the manner in which the heat and pressurearev applied. For example, the caul may be simply a polished metal platesuch as indicated at 3 in Fig. 4. The work may be placed under pressureand heat either in a press or by passing it between hot rolls. In Fig. 4the assembly is shown as disposed between the lower and upper platens Aand B of a hot press. Actually, when the'work is carried out in a hotpress, the upper platen maybe made to serve as the caul. At any rate,assuming that the press, or at least the upper platen thereof, be hotenough to heat pitch of C. melting point to a temperature of from aboutC. to 260 0., the press is closed on the work, causing the pitch to meltand to be driven completely into the fibrous rated.

material; the pressure being such that the fibrous material is slightlycompressed, the thickness of a three-quarter inch board being reduced inthe example given about one-sixteenth of an inch. The press remainsclosed on the workfor only a short time, say, from about forty-fiveseconds to four minutes. The pitch penetrates into the board or panel toa depth of about one-sixteenth of an inch, as indicated by the shadedarea 4 in Fig. 3.

when the pitch is applied in powdered form, it may conveniently bespread over the bottom platen of a press and be surrounded by a frame ofabout the same length and width as the panel and of a thickness aboutequal to the depth of the layer of pitch that is needed. Then, when theinsulation board is laid upon the pitch, the latter cannot scatter butis confined by the low frame-like barrier. Upon closing the press, themolten and partially vaporized pitch is still confined and substantiallyno loss of pitch results through leakage at the edges of a board orpanel. The opening in the frame surrounding the pitch on the lowerplaten of the press may be a little smaller than the size of the panel,so that the extreme marginal portions of the panel become compressed topermit the panel to be forced down into contact with the bed of thepress. This insures a good seal between the frame and the board or paneland causes no damage to the latter because the board or panel is alwaystrimmed afterwards.

If a hardened stratum is desired on both sides of a board or panel, itis only necessary to place a secondlayer of pitch between the under sideof the panel in Fig. 4 and the underlying caul which may be a platesimilar to the plate 3 or may be the lower platen A of the press. Inthat event, a second indurated stratum is created at the lower face ofthe board or panel, as indicated at 5 in Fig. 6. A board of the lowdensity fibrous insulation board type treated in the manner justdescribed is about twice as stiff as, and possesses about fifty percentgreater bending strength than, a similar untreated board.

In order to cool each board or panel while it is held in a fiatcondition, I transfer it from the hot press directly to a cold press,not shown,

and leave it in the latter until the assembly has cooled and the pitchhas become hard.

In Fig. 5 there is illustrated a section of the wall of a building inwhich my improved boards or panels are secured directly to the studs andthus take the place of the usual sheathing as well as the siding orfacing material; the indurated sides of the boards or panels beingexposed to the weather if only one side of each has been indu- Byemploying the overlapping, jointforming parts of meeting boards orpanels, as explained in my prior application, Serial No. 301,- 143, thecombination sheathing and siding may be nailed to the studs withoutleaving any signs of nails on the exterior, if the panels are made justwide enough to span the distance between adjacent studs. In other words,one of the boards or panels may be provided with a long tongue 6 lyingflat against the stud 1 and secured thereto by nails 8. The meetingboard or panel is shaped along the margin to overlie the tongue 6 and,preferably, otherwise to interlock with the panel that has been nailedto the stud, so that it cannot become loose or be separated from thecooperating panel after its flange or lip 6 has, in turn, been nailed tothe next stud; further security of the joint being attained by theintro- 75 duction of an adhesive or'a heavy paint between the meetingsurfaces as explained in my aforesaid application.

In Fig. 7 there is illustrated a board or panel 5 comprising a core 8 ofwood and facings l0 and ll of paper. Paper treated in accordance with myimproved process may be used to advantage for the facings of this typeof lumber. Paper may be treated by a continuous process so that 10 thecost of the treatment is not much greater than that of the pitchrequired. Paper may conveniently be treated two sheets at a time. Thus,for example, in Fig. 8, there is illustrated a roll I! of paper I3 whichis carried between sets of hot rollers l4 together with an overlyingsheet ii that is drawn progressively from a roll ii. If the pitch is tobe applied progressively as the sheets are fed ahead, a section of thesheet B may be left exposed in advance of the point where this sheetmeets the sheet 15, so that the pitch While I have referred only to theuse of powdered pitch, the pitch may be applied to the boards and thesheets in any desired way. Also, where powdered pitch is employed, itmay be caused to melt more or less before undergoing the tlnai heat andpressing operation to insure that the even distribution of the pitchwill not be disturbed. In the case of the paper sheets, they need onlybe drawn over heated rolls, with the pow- 0 dered pitch lying on top ofthe sheets, in order to cause sumcient melting to hold the pitch inplace. The pitch may be caused to form a coating adhering to the paperwith sufllcient tenacity to permit the paper to be rolled up until it isdesired to carry out the final impregnating step.

In the process of impregnating paper sheets, approximately the sametemperatures as employed in the case of boards or panels are required.The time required to complete the impregnation of sheet material isusually less than in the case of boards or panels. Thus, to indurate,through complete impregnation, sixteen point kraft paper, from fifteenseconds to sixty seconds are needed, when plate pressure is used.

While I have illustrated and described my invention with considerableparticularity, I do not desire to be limited to all of the details thusillustrated and described; but intend to cover the whole field ofinvention as the same is set forth in the following claims thatconstitute the definition of the invention.

I claim:

1. A fibrous board of the low density insulating board type havinghardwood pitch coating the fibers distributed throughout an outer layerof the board.

2. A fibrous board of the low density insulation board type havinghardwood pitch coating the fibers distributed throughout a layer ofsubstantial depth adjacent to each face of the board.

3. A thick board of the low density fibrous insulation board type havingthe fibers thereof coated with hardwood pitch for a. distance of about asixteenth of an inch inwardly from a face thereof.

4. A thick board of the low density, fibrous insulation board typehaving the fibers thereof coated with hardwood pitch for a shortdistance inwardly from each face thereof and being about twice as stiffas and possessing about fifty percent greater bending strength than asimilar untreated board.

5. The method of indurating a body of fibrous porous material, for ashort distance below a surface thereof which consists in covering thesurface thereof with wood pitch, pressing the assembly between hotplates, and causing the pitch to melt and to be partly converted intofumes.

6. The method of indurating a porous board of fibrous material, whichconsists in applying to a face thereof a layer of wood pitch, andapplying to the pitch, through a vapor-retaining covering member,pressure and sufilcient heat to melt the pitch and to be partlyconvertedinto/ fumes.

'7. The method of indurating a porous board of fibrous material, whichconsists in placing upon a face thereof a layer of hardwood pitch, andsubjecting the board to heat and pressure applied through a memberhaving an imperforate face spanning the length and breadth of the board.

8. The method of indurating a board of fibrous porous material, whichconsists in placing upon a face thereof a layer of hardwood pitch,covering the pitch with a caul, and applying through the can] pressureand sufficient heat to melt the pitch andto cause it to :be partlyconverted into fumes.

9. The method of indurating a board of the fibrous porous insulationboard type, which comv prises placing on a face thereof a layer ofhardwood pitch having a melting. point of from 105 C, to 110 C., andheating the pitch to a temperature substantially above 160 'C. whilepressing it against the board and preventing the escape of most of thefumes into which some of the pitch is transformed.

10. The method of indurating a board of the fibrous porous insulationboard type, which comprises placing on a face thereof a layer ofhardwood pitch having a melting point of from 90 C. to 100 0., andheating the pitch to a temperature -a,sia,as1

substantially above 'C. while pressing the same against the board andpreventing the escape of most of the fumes into which some of the pitchis transformed.

11. The method of indurating a board of the fibrous porousinsulationboardtype. which comprises covering a face thereof with a lyer of hardwood pitch, causing the pitch to m it and to be partlyconverted into fumes while confined in contact with and pressed-againstthe board, and then cooling the :boardwhile constraining it in thedesired shape.

12. The method of indurating a board of the fibrous porous insulatingboard type, which comprises covering a face of the'board with a layer ofhardwood pitch, andplacing the assembly in a hot press and subjecting itto some pressure and to a temperature of at least C. for a period offrom about forty-five seconds to four minutes.

13. The method of indurating a board ofthe fibrous porous insulationboard type, which comprises covering a face of the board with powderedhardwood pitch having a melting point of from 105 C. to 110 C., placingon the pitcheovered face an'imperforate metal plate, sub. jecting theassembly to pressure and to a temperature of from C. to 260 C., and thentransferring it to 'a cold press.

' 14. The method of indurating a three-quarter inch board of the fibrousinsulation board type, which comprises covering a face of the board witha layer of powdered hardwood pitch about one tenth of an inch thick,placing the assembly in a press and subjecting it for a period of from-15. The method of indurating fibrous porous sheet material with woodpitch, which comprises laying two such sheets upon each other with alayer of pitch between them, subjecting the assembly to pressure andheating it to a temperature sufiicient to melt the pitch and convert itpartially into fumes, and then separating the sheets from each other.

I ARMIN ELMENDORF.

